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[Mark Wilkinson]

Here's snip of a pair of Orbit Shifters indoors. 
Close mic'ed, raw response except for a +4db boost at 47hz.
My question is:  given the fairly steep natural rolloff below about 35hz, is a HP filter really necessary?
I've always used one, a BW4 @25...but not really sure why other than 'supposed to'....
Thx,  Mark

[Ivan Beaver]

In my opinion EVERY LOUDSPEAKER should use a HP filter-no matter what the response is.

The reason is that freq below when it can "easily work", the driver will tend to "flop around".

This can easily cause physical damage to the driver-even if the power is less than the ratings.

Even if the signal does not contain those freq, there are all sorts of "things" that can cause freq lower than intended to get to the driver.

Loose connections, people hot plugging something etc.

It is far better to be safe-rather than sorry.

[Paul G. OBrien]

Below port tuning or horn loading the driver is no longer damped by the enclosure meaning it operates as if it was out of the box hanging in free air and could be driven to it's mechanical limits with relatively little power, so if you want to keep your drivers functional you would be well advised to always have a low cut/high pass filter engaged.

[Mark Wilkinson]

Thx guys,

I get what you're saying and have always told myself the same considerations.
Please do know I'm only asking about this particular horn loaded sub, and for when it is properly powered/ limited.....

Looking at the trace comparisons below, blue is raw, and purple is with a BW24 HP @30hz and a LR48 LP @ 100hz.
Sure HP rolls off faster, but it doesn't seem to add that much protection, .....
.....and the protection comes at the expense of either a bunch more phase rotation or latency, whichever poison is chosen..(latency in this example, note the unchanged phase traces)

I'm interested in dropping the HP because the most credible literature I can find on phase audibility, says best sound comes from linear phase throughout except for system high-pass, which equates to sub high pass. 
Supposedly, getting phase to follow sub magnitude roll-off is ideal.  IOW if magnitude rolls off at 24 db/oct, phase should rotate at same 4 pole rate per octave.

Want to find out for myself...and at crankin volume 

[David Allred]

Just because it can't produce 5hz, doesn't mean it ain't trying.

[John Halliburton]

All good reasons.  The Orbit Shifter(and any other sealed back/rear enclosure design) will offer some resistance to out of bandwidth response, but it is still a wise thing to have a good high pass filter in the circuit. 

One other benefit is that it should help lower nonlinear distortion should the driver be in the situation of reproducing that  20hz organ pedal note along with the content within it's design capacity.

Best regards,

John

[Tim McCulloch]

Here's snip of a pair of Orbit Shifters indoors. 
Close mic'ed, raw response except for a +4db boost at 47hz.
My question is:  given the fairly steep natural rolloff below about 35hz, is a HP filter really necessary?
I've always used one, a BW4 @25...but not really sure why other than 'supposed to'....
Thx,  Mark

Yes. Use the Filter, young Skywalker.

[Ivan Beaver]

Thx guys,

I get what you're saying and have always told myself the same considerations.
Please do know I'm only asking about this particular horn loaded sub, and for when it is properly powered/ limited.....

Looking at the trace comparisons below, blue is raw, and purple is with a BW24 HP @30hz and a LR48 LP @ 100hz.
Sure HP rolls off faster, but it doesn't seem to add that much protection, .....
.....and the protection comes at the expense of either a bunch more phase rotation or latency, whichever poison is chosen..(latency in this example, note the unchanged phase traces)

I'm interested in dropping the HP because the most credible literature I can find on phase audibility, says best sound comes from linear phase throughout except for system high-pass, which equates to sub high pass. 
Supposedly, getting phase to follow sub magnitude roll-off is ideal.  IOW if magnitude rolls off at 24 db/oct, phase should rotate at same 4 pole rate per octave.

Want to find out for myself...and at crankin volume 

The real answer is "it depends".

I do agree that the best sonic performace will be without a HP filter.

HOWEVER-if you want to push the system hard, the additional protection of the HP filter far outweighs any sonic advantage-ESPECIALLY when the driver STOPS WORKING because it has "beat itself to death".

I am sure that "all of the people in the audience" will "understand" that earlier they were enjoying a better sonic performance, and now there is no bass.

People who have been drinking are very understanding in that regard

I am sure that the club owner will not mind if people stop drinking and leave because there is no bass anymore.

After all, it sounded so good earlier, it more than makes up for the lack of bass now.

YES, I am being sarcastic, but also being very real.

Sometimes it is more important to keep the system working, than to get a "little bit more" out of it and then have it fail.

I remember back in the early 80s, working with a Metal band.

Everything was going great, but the band wanted a little bit more out of the system.  They said they would pay for any blown speakers.

That may be all well and good, but at midnight on a Saturday-what am I going to do to get new drivers in the cabinets to play till 2am?

If I pushed the system and it stopped, they would QUICKLY forget all about the "we will pay for new speakers" and get mad at me for killing the system.

Then they and myself would not be hired back in the club because the system died.

None of the audience was complaining-just a couple of guys in the band.

It was simply not worth the risk.

Just something to consider.

I still say "ALWAYS use a properly set high pass filter".  The possibility of damage is simply not worth it.  Unless you are doing low to mid level listening.

[David Allred]

Everything was going great, but the band wanted a little bit more out of the system.  They said they would pay for any blown speakers.

Even if they survive the night, the damage may be done and not show itself for days, weeks, or months.  Get cash payment up front as a non-refundable deposit.

[Mark Wilkinson]

Hey thanks all....I feel the experience/wisdom...HP in 

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